Vehicle comprising a pane bonded to the bodywork

ABSTRACT

A vehicle including at least one glass pane, bodywork, and at least one layer of viscoelastic material interposed between the glass pane and the bodywork.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.12/972,136, filed Dec. 17, 2010, which is a continuation of U.S.application Ser. No. 12/774,124, filed May 5, 2010, which claims thebenefit of priority from U.S. application Ser. No. 12/567,967, filedSep. 28, 2009, the entire contents of which is incorporated herein byreference. U.S. Ser. No. 12/567,967 is a continuation of U.S.application Ser. No. 11/719,446, filed May 16, 2007, which is a NationalStage of PCT/FR05/50955, filed Nov. 16, 2005, and in turn claimspriority to FR 04 12121, filed on Nov. 16, 2004.

The invention relates to vehicles comprising at least one glass pane andbodywork.

Under the effect of excitations generated by the engine and the contactof the tires with the carriageway, the windshield and the rear window ofan automotive vehicle may become significant noise transmitters below afrequency of 800 Hz. Generally, when a windshield is vibrated by itsmechanical supports or by an incident acoustic wave, it generatespressure waves that are transmitted through the passenger compartment tothe detriment of the comfort of the passengers.

In order to improve the acoustic performance of automotive vehicles, thereduction of the vibrational level of these two panels, amongst otherthings, is the subject of many studies. Currently, two types ofsolutions are adopted.

The first consists in strengthening the body structure in order todecrease the propagation of the vibrational energy toward these panels.The effectiveness of this solution is limited by architecturalconstraints. This solution also results in an increase in the weight andcost of the body.

Another solution consists of a damping material of polyvinyl butyral(PVB) type. Indeed, windshields are known today that are made from thismaterial, which was developed to shift the glass transition temperaturetoward 15° C. With this characteristic, the windshield has a highdamping factor at room temperature. On the other hand, this solution hastwo drawbacks. On the one hand, its vibration-attenuating effect onlybecomes significant above 150 Hz, as below this frequency thedeformation of the windshield prevents the PVB from working further. Onthe other hand, it represents a significant overcost (more than 10ε)relative to a conventional windshield.

One objective of the invention is to improve the comfort of the vehicleoccupants.

With a view to achieving this objective, a vehicle is provided accordingto the invention that comprises at least one glass pane and bodywork,and at least one layer of viscoelastic material interposed between theglass pane and the bodywork.

Thus, when an incident wave or an excitation generates a vibration ofthe windshield, this vibration is transmitted to the viscoelasticmaterial which converts some of this wave into mechanical strain energyand into heat energy. The vibration of the windshield is thereforegreatly attenuated, which improves the comfort of the passengers.

The vehicle according to the invention could have, in addition, at leastone of the following features:

-   -   the viscoelastic material extends continuously along at least        one side of one perimeter of the glass pane;    -   the viscoelastic material extends discontinuously along at least        one side of one perimeter of the glass pane;    -   the glass pane has a perimeter of which at least one side is        free from viscoelastic material;    -   it comprises, in addition, at least one layer of adhesive        interposed between the glass pane and the bodywork;    -   it comprises at least one area in which the layer of adhesive        and the layer of viscoelastic material are superposed;    -   it comprises at least one area in which the layer of adhesive        and the layer of viscoelastic material are superposed, this area        comprising, in addition, a layer of adhesive or of viscoelastic        material juxtaposed with the superposed layers;    -   it comprises a film interposed between the superposed layers;    -   it comprises at least one area in which the layer of        viscoelastic material and a layer of adhesive are juxtaposed;        and    -   the viscoelastic material has the following characteristics:        -   a loss factor greater than or equal to 0.7; and        -   a elastic shear modulus less than or equal to 3 MPa,            in a temperature range from 10 to 40° C. and under a            vibrational excitation between 20 and 500 Hz.

Also provided according to the invention is a process for attaching atleast one glass pane to vehicle bodywork, in which one layer ofviscoelastic material is interposed between the glass pane and thebodywork.

Other features and advantages of the invention will become more apparenton reading the following several embodiments given by way of nonlimitingexamples, with reference to the appended drawings in which:

FIG. 1 is a plan view of a vehicle according to a first embodiment ofthe invention, at the level of the windshield and its attachment to thebodywork;

FIG. 2 is a cross-sectional view of the vehicle from FIG. 1 along theplane II-II;

FIGS. 3 and 4 are similar views to FIG. 1 illustrating otherembodiments;

FIGS. 5 to 8 are similar views to FIG. 2 illustrating other embodiments;

FIG. 9 is a similar view to FIG. 1 illustrating another embodiment;

FIGS. 10 to 12 are cross-sectional views of the vehicle from FIG. 9along the planes X-X to XII-XII respectively;

FIGS. 13 and 14 are similar views to FIG. 2 illustrating otherembodiments;

FIG. 15 is a plan view of the embodiment illustrated in FIG. 14 whichconstitutes a cross section along the plane XIV-XIV of the arrangementfrom FIG. 15;

FIG. 16 is a cross-sectional view of the embodiment from FIG. 15 alongthe plane XVI-XVI; and

FIGS. 17 to 19 illustrate other embodiments.

A first embodiment of the vehicle according to the invention isillustrated in FIGS. 1 and 2. The vehicle comprises several glass panesamong which is a windshield 2. The invention will be described inrelation to the windshield in the embodiments below. Nevertheless, it isclearly understood that the invention could be used with other glasspanes such as the rear window.

The vehicle comprises a bodywork 4 comprising, in particular, two struts6 made of metal or of plastic to which the windshield 2 is attached. Forthis purpose, a layer of standard adhesive 8 such as an adhesive knownas HV3 and sold under the brand GURITE is provided, which conventionallyensures bonding of the windshield to the body. The transverse section ofthe layer 8 has, for example, a thickness of 4 mm and a width of 6 mmand its elastic modulus is between 30 and 50 MPa.

The arrangement also comprises a layer of an elastic or viscoelasticmaterial 10. This layer has, in this particular case, a thickness of 1to 2 mm. The term “viscoelastic material” is understood to mean amaterial whose elastic modulus is between 1 and 3 MPa and whose lossfactor is greater than 0.7, for example around 10. A material such asbutyl rubber could be chosen. The layers 8 and 10 are superposed hereand form, with the windshield 2 and the two sheet layers forming thebodywork, a multilayer of five layers as illustrated in FIG. 2.Specifically, the upper face of the adhesive layer 8 spreads out incontact with the lower face of the windshield 2. The lower face of theadhesive layer 8 spreads out in contact with the upper face of the layer10 of viscoelastic material. The latter spreads out in contact, via itslower face, with the bodywork 4. A lip seal 12 is provided that coverson the one hand the edge of the windshield 2, which otherwise wouldextend toward the bodywork, and on the other hand the edge of thewindshield strut.

As can be seen in FIG. 1, the assembly formed by superposing the twolayers forms four portions corresponding respectively to the four sidesof the perimeter of the windshield 2. For each side, the correspondingportion extends continuously over a larger part of this side, in itscentral area.

In this arrangement, the adhesive 8 ensures bonding of the windshield tothe body while the layer of viscoelastic material 10 makes it possibleto dissipate the energy transmitted between the body and the windshield.In order to dissipate the maximum amount of energy, the ratio of theelastic moduli between the adhesive and the viscoelastic material willpreferably be greater than 5. In the embodiments described, it is theshear loss factor which is to be considered. This variation in thestiffness makes it possible to transmit energy to the layer ofviscoelastic material and make the latter work, especially in shear.Another factor which may be important is the discontinuity of theplacement of the viscoelastic material around the windshield insofar asthe aforementioned portions are not in contact with one another. Indeed,this discontinuity may artificially create local deformations thatamplify the dissipation effect of the material.

This effect could be accentuated by providing, as a variant, as in FIG.3, in which each portion is formed from a continuous adhesive layer 8covering the discontinuous sections of the viscoelastic material layer.The viscoelastic material layer 10 is therefore discontinuous this time.In the embodiment in FIG. 3 the windshield 2 is attached to the bodyworkonly by its upper and lower longitudinal sides by means of thisarrangement.

With reference to FIG. 4, it could be planned, in another embodiment,that the superposition of the two layers 8 and 10 takes place over theentire perimeter of the windshield to form a continuous double-thicknessbead. This arrangement has the advantage of improving the sealingbetween the windshield and the bodywork and makes it possible,optionally, to dispense with a seal specifically for that purpose.

In another embodiment illustrated in FIG. 5, a film or a foil, made ofplastic or of metal for example is interposed between the layers 8 and10. This film 20 has the role of strengthening the adhesion between thelayers 8 and 10 and of amplifying the shear of the viscoelastic material10.

In the arrangement provided in FIG. 6, by way of foil 20, a clip orclamp 26 is used of which one part extends between the layers 8 and 10and which covers the edge 28 of the parts forming the bodywork in orderto be attached via its side opposite to one face of these parts that isopposite to the layer 10.

As the embodiments in FIGS. 7 and 8 show, it is also possible toenvisage increasing the number of superposed layers. Thus, in theembodiment in FIG. 7, an additional layer of viscoelastic material 22 isinterposed between the upper face of the adhesive layer 8 and the lowerface of the windshield. The adhesive layer 8 is therefore interposedbetween two viscoelastic material layers. Conversely, in the embodimentprovided in FIG. 8, it is an additional layer of adhesive 24 that isprovided between the lower face of the viscoelastic material layer 10and the bodywork, so that the viscoelastic material layer 10 isinterposed this time between two adhesive layers. Further increasing thenumber of superposed layers could also be anticipated.

In the embodiment in FIG. 9, the attachment of the windshield 2 to thebodywork 4 is carried out in two different ways correspondingrespectively to the areas 40 and 42. The first areas 40 correspondapproximately in the present example to the left and right lateral sidesof the windshield while slightly covering the lower and upperlongitudinal sides. The second areas 42 correspond in the most part tothe upper and lower sides. The structure of the areas 40 is illustratedin cross section in FIG. 11. In these areas, the windshield is attachedto the bodywork by means of the single adhesive layer 8 which istherefore in direct contact with the lower face of the windshield andthe bodywork. In the second areas 42, as illustrated in FIG. 10, thewindshield is attached to the bodywork by means of an arrangementsimilar to that already described with reference to FIG. 5 although theviscoelastic material is this time located above the adhesive 8.

Again, the viscoelastic material makes it possible to absorb thevibrational energy transmitted between the bodywork and the windshieldto ensure a good antinoise performance. Nevertheless, as good qualitybonding of the glass pane to the bodywork is not necessarily ensured,especially due to the lack of flatness of the rebates supporting thewindshield, it is preferable to superpose it, in addition, onconventional adhesive, optionally under a smaller thickness than normal.The separating foil ensures sufficient adhesion at the interface betweenthe viscoelastic material and this adhesive. In the case where theviscoelastic material is compatible with suitable adhesion at theinterface, this separating foil will not be necessary. In the areas 42,the adhesive has, in particular, the role of making up for thegeometrical irregularities of the bodywork to ensure bonding and sealingthat conform to the recommendations. In order to absorb the maximumamount of vibrational energy transmitted between the bodywork and thewindshield, it will be preferable for the viscoelastic material to havea large loss factor and a low shear modulus in the frequency bandconcerned. It is possible to use the following values as referencevalues:

-   -   temperature range: from 10° C. to 40° C.;    -   frequency: from 20 to 500 Hz    -   loss factor: greater than 0.7; and    -   elastic shear modulus: less than 3 MPa (10⁶ N/m²).

By way of example, acrylic foams are materials that can meet theserequirements.

Besides the acoustic performance, the viscoelastic material must meetthe mechanical strength criterion in case of impact. It is known,especially in the case of a frontal impact, that the driver andpassenger airbags are deployed and exert a large force on the bottom ofthe windshield. In order to ensure the mechanical strength of thewindshield in case of impact the viscoelastic material will preferablyhave to meet the specifications for the breaking stress being greaterthan 3 MPa. Indeed, the deployment time of an airbag is of the order ofa few tenths of a second with a deformation of the elastic material ofaround a millimeter. The speed of the impact is therefore equivalent toa vibrational frequency greater than 1000 Hz. Thanks to its highviscosity, the viscoelastic material has a very high resistance to rapiddeformation. For example, for the material sold under the nameSCOTCHDAMP SJ-2001 5X Viscoelastic Polymer, at 20° C., the modulus is 20MPa and it is greater than 5 MPa at 1000 Hz. Consequently, this type ofmaterial meets both the vibrational demands and those of passivesecurity.

To ensure suitable sealing of the windshield, it will be preferable toavoid a sudden discontinuity at the junctions between the areas 40 and42. It is therefore possible to produce a junction as illustrated inFIG. 12. From this it can be seen that the thickness of the adhesivelayer 8 gradually increases as the thickness of the viscoelasticmaterial layer 10 decreases and this following a linear progression tothe boundary between the areas 40 and 42.

It will be possible to provide that the pressing device used forpositioning the viscoelastic material shapes the product so that its endhas a tapered shape approaching that of FIG. 12. However, in the casewhere this tapering of the material will not be sufficient, it will bepossible to provide an excess of adhesive at the joining point with theother material. This excess will possibly be attained by slowing downthe device for depositing the adhesive which will deposit therein anincreased amount in order to guarantee sealing in this fragile area. Inthe embodiment in FIG. 12, it could be provided that the adhesive is ofthe type DOW HV3.

Another embodiment has been described in FIGS. 14 to 16. This time, incertain areas 52 (for example, corresponding to areas 42), thewindshield 2 is attached to the bodywork 4 by means of the adhesive 8and the viscoelastic material 10 while, in the other areas 50 it isattached thereto only by means of the adhesive. Contrary to theembodiment in FIG. 9, in the areas 52, the two layers 8 and 10 are thistime juxtaposed and at a distance from one another. They are placed oneby the side of the other each in contact with the lower face of thewindshield. They are moreover each in contact with the bodywork, ashoulder 54 possibly being provided at the rebate for taking intoaccount the fact that the thickness of the viscoelastic material layer10 is less than the thickness of the adhesive layer 8. This solutionmakes it possible to produce a continuous loop of adhesive over theentire periphery of the windshield. As the shear modulus of the adhesiveis higher than that of the viscoelastic material, it is preferable toincrease the thickness of the adhesive layer and to decrease the widththereof in the areas 52 in comparison to the areas 50 in order tomaintain the effectiveness of the viscoelastic material. The thicknessesand widths of the layers of adhesive and of viscoelastic material aredetermined by calculations that enable the shear strain energy of theviscoelastic material to be maximized. Thus, in the or each area 52, thebonding line is narrower and thicker. The robot that carries out bondingof the windshield in the assembly line may therefore keep the same speedand the same adhesive delivery flow rate, which simplifies the assemblyprocess.

In another embodiment, the seal 12 of FIG. 2 could be replaced with aseal that makes it possible to seal between the windshield and thebodywork regardless of the arrangement adopted for the adhesive andviscoelastic material layers. Such an arrangement makes it possible notonly to simplify the junction between the two areas 50 and 52 but alsoto leave more freedom for optimizing the damping device and improvingits performance.

For example, it will be possible to provide embodiments such as thoseillustrated in FIGS. 17 and 18. In FIG. 17, the lower longitudinal sideof the windshield is made up of an area 62 in which the layers arecontinuous and have the arrangement from FIG. 5 whereas they arediscontinuous along the upper longitudinal edge 64 of the windshieldwith the same arrangement. The left and right lateral sides of thewindshield are free of layers.

In the embodiment from FIG. 18, it is the two upper and lowerlongitudinal sides of the windshield that are provided with a doublediscontinuous layer.

Finally, in the embodiment from FIG. 19, the windshield is attached tothe bodywork by means of a continuous viscoelastic layer 10 forming aloop corresponding to the entire perimeter of the windshield. At theleft and right lateral sides, an adhesive layer 8 is juxtaposed with theviscoelastic layer 10, so that this layer is also in contact with thebodywork and the windshield. A space is formed between the viscoelasticmaterial layer and the adhesive layer. In order to ensure good acousticperformance, it will be anticipated that the modulus of the viscoelasticmaterial is relatively low. This is why it will be possible to keep thetwo standard adhesive strips with a high elastic modulus greater than 20MPa. During twisting of the body, it is the adhesive at the side strutsthat undergoes the highest loading level. This is the reason thisarrangement is provided for placement of the adhesive. In summary, thecomplete loop of the viscoelastic material ensures the acousticperformance and sealing while the standard adhesive restricted to thetwo lateral sides ensures the mechanical strength.

Generally, before positioning the viscoelastic material, it will beadvantageous to prepare the glass pane over the whole of its perimeterfor bonding by application of a primer in a known way. The viscoelasticmaterial is protected on one face by a nonstick protective strip and iswound onto itself being in the form of a roll. A device providing therole of a reel and of peeling off the protective strip is used toposition the product onto the areas described above of the groove forbonding the glass pane and/or the bodywork. Squeezing of theviscoelastic material is provided at the same time as the positioning bythe action of a pressure roller, the force of which will be tared as afunction of the recommendations characteristic of the viscoelasticmaterial. Typically, the adhesive is applied after the viscoelasticmaterial.

If the viscoelastic material is not compatible with the glazingadhesive, it will be possible to provide, as previously mentioned, afoil, for example in the form of a PET material having a thickness ofaround 10 micrometers. This foil could be treated in order to have agood bondability with regards to the glazing adhesive. This treatmentcould be carried out by an adhesion primer such as, for example,BETAPRIME 5404 from Dow.

The adhesive for positioning the glazing is deposited over the wholebonding groove while respecting the total height specified, whether thisis in the areas where the viscoelastic material is present or outsidethese areas. The adjustment of the amount of adhesive as a function ofthe area will be obtained by a variation in the speed of the bondingrobot, for example.

The invention in its various embodiments makes it possible to reduce theamplitude of the vibrations of the windshield by introducing dampingthanks to a particularly advantageous geometry and process and also anattachment that amplifies and concentrates the incident energy in orderto better dissipate it. The adhesive corrects the manufacturingvariations and the surface irregularities during the attachment.

It should be noted that in FIGS. 1 to 10, 12, 17 and 18, theviscoelastic layer, for example in the form of a strip adhering to thetwo faces, is in series with the adhesive layer. In FIGS. 19, 14 and 15,the viscoelastic layer is in parallel with the adhesive layer. In thiscase, the viscoelastic material is, for example, applied in the form ofa paste to make it easier to compensate for the surface irregularities.In FIG. 13, application of the layers is a combination of application inseries and in parallel.

Of course, it will be possible to introduce numerous modifications tothe invention without going outside the scope thereof.

It could be anticipated, as illustrated in FIG. 13, that one layer ofadhesive (or of viscoelastic material) 70 is juxtaposed with twosuperposed layers of adhesive 8 and of viscoelastic material 10, andthis being at least in certain areas of the perimeter of the windshield.

1. A vehicle, comprising: at least one glass pane; bodywork; and atleast one layer of viscoelastic material interposed between the glasspane and the bodywork.
 2. The vehicle as claimed claim 1, wherein theviscoelastic material extends continuously along at least one side ofone perimeter of the at least one glass pane.
 3. The vehicle as claimedin claim 1, wherein the viscoelastic material extends discontinuouslyalong at least one side of one perimeter of the at least one glass pane.4. The vehicle as claimed in claim 1, wherein the at least one glasspane has a perimeter of which at least one side is free fromviscoelastic material.
 5. The vehicle as claimed in claim 1, furthercomprising at least one layer of adhesive interposed between the atleast one glass pane and the bodywork.
 6. The vehicle as claimed inclaim 5, further comprising at least one area in which the at least onelayer of adhesive and the at least one layer of viscoelastic materialare superposed.
 7. The vehicle as claimed in claim 5, further comprisingat least one area in which the at least one layer of adhesive and the atleast one layer of viscoelastic material are superposed, the at leastone area including a layer of adhesive or of viscoelastic materialjuxtaposed with the superposed layers.
 8. The vehicle as claimed inclaim 6, further comprising a film interposed between the superposedlayers.
 9. The vehicle as claimed in claim 1, further comprising atleast one area in which the at least one layer of viscoelastic materialand a layer of adhesive are juxtaposed.
 10. The vehicle as claimed inclaim 1, wherein the viscoelastic material has the followingcharacteristics: a loss factor greater than or equal to 0.7; and anelastic shear modulus less than or equal to 3 MPa, in a temperaturerange from 10 to 40° C. and under a vibration excitation between 20 and500 Hz.
 11. A process for attaching at least one glass pane to a vehiclebodywork, comprising: interposing a layer of viscoelastic materialbetween the at least one glass pane and the vehicle bodywork.
 12. Thevehicle as claimed in claim 6, further comprising at least one area inwhich the at least one layer of adhesive and the at least one layer ofviscoelastic material are superposed, the at least one area including alayer of adhesive or of viscoelastic material juxtaposed with thesuperposed layers.
 13. The vehicle as claimed in claim 7, furthercomprising a film interposed between the superposed layers.